Service providers are evolving the existing time division multiplexing (“TDM”) based circuited networks to packet-based networks and eventually to end-to-end internet protocol telephony applications using session initiation protocol (“SIP”) as the signaling protocol. A typical session initiation protocol network architecture may consist of one or more session initiation protocol back-to-back user agents (“B2BUA”) and session initiation protocol user agents (“UA”). The session initiation protocol user agents employ specific network protocol technologies to communicate with other network entities. The session initiation protocol user agents employ network negotiation to set up communication with other session initiation protocol user agents.
Several network configurations exist that require network negotiation. Exemplary configurations include internet protocol (“IP”) local area networks (“LANs”) connected through an asynchronous transfer mode (“ATM”) wide area network (“WAN”), internet protocol local area networks connected through an internet protocol wide area network, and an internet protocol local area network connected to a public switched telephone network (“PSTN”) through an internet protocol wide area network.
As one shortcoming, a session initiation protocol user agent employing one network protocol technology cannot directly communicate with a session initiation protocol user agent employing a different network protocol technology. Different session initiation protocol user agents may employ different network protocol technologies. For example, session initiation protocol user agents may support network protocol technologies such as internet protocol, asynchronous transfer mode, and time division multiplexing (“TDM”). Session initiation protocol employs session description protocol (“SDP”) offer/answer procedures to perform network negotiation between session initiation protocol user agents in a session initiation protocol network. If the session initiation protocol user agents do not support one or more common network protocol technologies, then session initiation protocol cannot successfully establish a communication session between the session initiation protocol user agents.
Thus, a need exists for enhanced network negotiation in a variety of network configurations.